Nonlinear variable resistance element



Dec. 19, 1933. K U 1,939,902

NONLINEAR VARIABLE RESISTANCE ELEMENT Filed Aug. 6. 1928 INVEN TOR.

BY QMMQMM ATTORNEY.

Patented Dec. 19, 1933 I NONLINEAR VARIABLE RESISTANCE ELEMENT John Km, Cincinnati,

Ohio, assignor to The Crosley Radio Corporation, Cincinnati, Ohio,

a corporation of Ohio Application August 6, 1928. Serial No. 297,843

Claims. (01. 201-55) My invention relates to variable resistance, the resistance of which varies as some function of the length of the resistance element.

-My object is more particularly to provide a 5 resistance element in which the arrangement is such that the proportionate change of resistance for a given amount of movement of the slider element or between taps at a given distance from the line side of the resistance will have a prear- 1 ranged value.

The invention consists essentially in modifying. the linear resistance of a wire or other resistance element by plating thereon the same or a different metal in a prearranged manner. It also consists in so plating that a tapered formation of the'deposit on the linear resistance element will give a difference of total resistance per unit of length which .changes in a prearranged gradual manner, thus cooperating with a moving element or slider so that a given movement of the slider will, at some parts of the resistance, effect less '01 a change than at other parts, which change can be made gradual and uniformly so.

I accomplish my objects by that certain structure of which an example will be hereinafter specifically described, and the novelty of which will be covered in the appended claims.

In the drawing:- Figure 1 is a diagram of a plating step. Figure 2 is a diagram illustrating a tapered deposit on a resistance wire.

Figure 3 is a diagram showing a like deposit made on a flat wound spiral.

Figure 4 is a plan view of a simple rheostat built 5 in accordance with my invention. I 1

Figure 5 is a side elevation of such a rheostat. Figure 6 is a sectional view of an alternative plating tank in operation.

It will be understood that my invention applies 40 to strips, wire, or other resistance elements, which may be straight or wound at the time that the electro-deposit is-built up thereon.

I have shown in Figure 1 a diagram of an electrolytic bath 1 in which are electrodes, say of copper, as at 2. A coil of resistance wire 3 is inserted at one end into the bath, and coupled with a conductor 4. The copper electrodesare coupled to aconductor 5. j

When plating is carried on in the manner indicated by passing a current through the bath, copper will be deposited upon the resistance wire. The deposit will, however, be heaviest at the end of the wire nearest to the attachment thereof to the conductor within the electrolyte, and will taper off upwardly (in the instance shown).

cathode.

By controlling the time of deposition I can provide a fairly .heavy coating of copper, in the example given, on the resistance wire at one end which tapers oii to a mere blush at the other end, whereupon the resistance element is withdrawn from the bath.

The manner of forming my special resistance member depends upon the initial resistance of the member itself. As is well known, when an electrolytic cell containing electrolyte and anodes is used for plating a cathode of low resistance, if the throwing power of the solution is satisfactory, a plating over the surface of the cathode may be obtained which to all intents and purposes is uniform. This sort of plating is what is ordinarily desired, but when plating is attempted on an element of high resistance, to which contact is made only at one end, there will be a shading oil of the current density passing into the electrolyte and through it to the anodes from varying portions 'of the cathode depending on the resistance of the portion of the cathode itself lying between the current connection and any given point in the If the cathode consists therefore of a length of wire (which is usually already wound upon an insulating support), the current density at the end of it next the current connection which is effective for the electrolyte plating action will be comparatively large, while it will shade of! rapidly from that point toward the other end of the cathode. Thus heavy deposits are obtained at the part adjacent the current connection and the deposit will shade oif toward the other end where, depending upon the time allowed for the electrodepositing action, it may be very small indeed or practically non-existent. A logarithmic resistance curve may be built up by means of this mode of deposit. r

Considering the resistance wire as a straight strand, I have indicated in Figure 2 the nature of the deposit, which is quite thick, at 6, and tapers gradually and proportionately in a linear manner down to the bare resistance element which may be said to be uncoated at '7. v

In Figure 3 I show the resistance element in a coil wherein the copper deposit is heaviest at the end 8, and tapers down to a mere blush, after which the resistance wire is uncoated.

Instead of plating on a wound resistance, I can plate on a bare wire, or I can plate on the wire in one wound condition and then re-wind it into another. By attaching conductors to various parts of a wire, wound or" straight, I can again control the nature of the deposit, tapering it, or

controlling it so that I vary the thickness and the 1. 'A linear resistance element having thereon taper at will. a tapered deposit of additional metal.

It will be understood that I can use any desired 2. A coiled linear conductor to be used as a reconductive resistance element, and any desired sistance, certain coils of saidconductor having a 5 metal to -plate"the'reon, which adds or detracts fcoa'tin'gof additional coiiductive'rnaterialtand cer- 80 from the resistanc efan'd tapersor not as I seefit. tain'of said'coils having on them successivelymore In particular my process is useful in obtaining. .conductive material than certain preceding coils. a truly and proportionately tapered deposit, there- 3. A conductor to be used in providing a variaby gaining cheaply an efiect which is quite expn' ble resistance comprising an electrically conducsive to obtain otherwise, requiring as it does a -.t ive' base elementof high resistance proportions 85 complicated mechanical arrangement wherebyffor Y and an electrically conductive coating on and l a given movement of the operating element, a' difelectrically continuous with said base. element, ferential movement is applied to the actualcontact having a 'plurality'fof variations in electrical conmember or slider, which engages the resistance fductivity "at intervals of its length, whereby the element or taps taken therefrom. resistance'of the conductor per unit of length is 90 In Figure 4 is shown a rheostat in whiehthe a modification of the inherent resistance of the flat wound resistance coil 8 is laid around a suitbase element per unit of length. able cylindrical barrel or housing which supports '4: A conductor to be used in providing a vaat its axis an arm 9. The arm has a slider 10 riable resistance comprismg n. electrically con- 0 thereon which wipes over theiresistance element. 'ductiVe'fbase .elerrie'ii'tfof. higliifresis'tangefpropqr- 95 Sofa1'-as'I am aware theprinciple of gradue tion'sand "an, electficallylcon uctive coatingon v 'atedde'p'ositsupona high resistancecathodehas and l tri u fflonfih ou limfh a basev mot hithertobeen'used topifoduce resistaneeeleinent, having. a plurality of variations inthickmerits which do not vary in a linear manner. I ness atjintervalsjofitslle g I x desire it to be understood that my invention is j, 5. A conductor""to .beluse providing a varia- 100 not therefore limited to platingupon wirepr p19r sistance oompfisingja nietal.,ba se element strands "ofl'resistance "elements but isfequally off highresistanceproportions andfametal coatd pt d ips, rto forrr'1 et l integralresistance on and electrically continuous with said base elements! 'Ihusaresistanceeieznentcomprising ele e t, having a plurality. .of var iations in a single'thin bar of'highresistance material may thi k es t i ter l 'pf it length, 5 be treated in a similar manners; If it be of metal 6. A variable @resistance'; deiiice comprising a itmay'be plated with the same metal so as to demetal wi'reand acontactf element to nialiagleccrease the resistance at one end thereof by a single trical contact therewithl'at different. intervals-of t c 'O t ay be platedwith adifierent its length, in which .the wire has thereon a coat.-

netafso'astc gain differe ltcffe ts, Again i not iiigv of 4 metal electrically continuous therewith 110 'of'metal' at all, it may l e-plated with metal so as and, so disposed thereon that the electrical' con to decrease its resistance-at "one end. The chief d ctivity'of jsaidconductor varieslat aiq d advantages of my invention aretworfirst, that ent intervals of itsleng'tln '1 r it iv s a ely qu c 'a ide y l tl i 7. n coileld electricaliconductorhaving thereon I securinganon-lin'ear resistance; 'which hasbeen ac iga'tingof conductive material electrically con- 115 rna'de'irfthe past only'with'great d fl q lt fi i tinuous therewith, in difierentamountson difusually by"t-'ne piecing together'of wariousfrngtcferent coils t eroorso as. to afiorda plurality of rials 'ofdiifering resistance. jsecondgljainlable variationscfelectrical conductivity otsaidmqnto produc'resistance elements'which dong]: have ducto'r from onecoil to another,- I al'inear variation but which nevertheless canbe 8. A coiled metal. wire havingl ,qn one] ts 120 varied -snioothly sincethere are no quick jumps in coils a coating' of 'i'netal electrically-,continuws y l' me r m-a a hig cs s ance t therewith and having on another one of. itscoils an b fi y O res tan e:;..'. a coatin'glof inetalfelectrically.continuous there- I have'shown'infFigure 1 a plating stepi'n which with, greater in amountlthanthecoating .on the the'IeSiStanCe member is notfe'ntirely immersed ill ongcqil sp as to varythe electrical conductivity 125 the ectrol t This'is convenient Where dc.- of said'conductorfrom one coil to the other, and

DOS-it is dsilfid'at'one end i511? el mc b an electrical contact element -niovable from one plating can also be carried onas shown in'Figure coil to'the'other, I 6 where the entire element is imm d h 9. A coiled electrical conductor'havinga ,coatthe quantityo'f deposit on the end of the element ing of conductive 'material thereon, electrically 130 furthest from the current connection will be procontinuous therewith, on a number of coils less portioned to the resistance of the element, the th? ll number of 00115 h vary ng i electromotive force impressed upon it, and the am on the Several sth 3 9 5???- length of'time it remains in the electrolyte. I devoid of t w fl f e 60 'Suitableconductors and suitable insulation, as non of electncal conductlvlty m lL- aFQ 13 will be understood without illustration, will carry A Variable resistance device cmprisin-g a i l conductor and a contact element to make eleca line connection to one end of the res.soance ele trical Contact. therewith at different interval-svof ment the load connection being made to the slidits length, in which a portion of the conductor er. Otherwise, as illustrated, the resistance elewith which the Contact elmenymak-esl dntact D ment may be connected across a line, such as for has a coating of conductiv-- material thereon example, the antenna circuit 01' a radio receiver, electrically cbntinuous therewithf 'fi h using terminals 11 and insulated m the amount at intervals of the le'ngthlof said porframe of the structure, and the Slider may be tion,'and another portion of said conductor with metallic and contact with the frame of the struch h said t t element makes t t is i and connected, y, to a Point Of e void of coating, so as to'aifo'rd a plurality of va-' ground potential in the radio receiver. riations of electric l conductivity of the conduc- Having thus described my invention, what I tor in successive portions with which the contact claim as new and desire to secure by Letters element makes contact.

Patent, isr- JOHN KAUL. 15o 

